In the past, there has been a control device that monitors a power outage state of a power supply device in a system and outputs a blackout signal at the time of power outage to cause a control target device to execute power outage process. Such a control device is mounted removably on a system substrate via a connector of the control device to allow removing for maintenance, inspection, and the like. Another device in the system determines whether or not the control device is removed by the presence of electrical connection of a signal line to recognize that the control device is mounted on the substrate.
As a related technique in the past, there is, for example, a technique that detects a voltage decrease of a commercial power supply, insulates the detection signal for incorporation, and obtains a switch output to a power supply in a battery switch circuit when the incorporated detection signal is applied and also a secondary output of an AC/DC convert starts decreasing. In addition, there is a technique that calculates a power outage detection value based on a load current value.
Japanese Laid-open Patent Publication No. 2006-33997 and Japanese Laid-open Patent Publication No. 2008-148495 are examples of the related art.
However, in the techniques in the past, when removing a control device for maintenance, inspection, and the like, there is a case of disconnecting electrical connection of a signal line for a control device to detect a power outage state of a power supply device before disconnecting electrical connection of a signal line for another device to recognize the control device. In this case, only by removing a control device for maintenance, inspection, and the like, power outage process sometimes turns out to be carried out by a control target device that has accepted a blackout signal from the control device.
It is desired to provide a control device, a control method, and a system that avoids execution of useless power outage process.